A typical example of a known method of transmitting an electronic television program guide is disclosed in "Protocol for a TV-Guide using Electronic Data Transmission, Draft 1", EACEM Technical Report No.11, August 1995. In this prior-art method, a plurality of data items such as start time, stop time, title, etc. of television programs to be broadcast are transmitted by one or more television stations.
In order to allow a variety of broadcasts and decoders to be developed, the concept of "Type of Electronic Program Guide (EPG)" has been introduced. EPG type-1 information transmitted on a television channel merely provides the transmission of What's Now and What's Next on the respective TV channel. EPG type-2 information comprises the data items for today's and tomorrow's television programs on this channel. EPG type-3 information covers a larger period of time and includes the data items of other television channels as well. EPG type-3 information includes auxiliary data to instruct a receiver to display the TV guide in a format determined by the information provider and to allow the user to navigate through the TV guide in a manner specified by the information provider. EPG type-3 transmissions are the most attractive from the information provider's point of view. They have the greatest similarity with the current printed versions of TV guides and allow the information provider to present his guide in a self-defined, easy-to-recognize, private "house" style.
At the receiver end, EPG decoders may also have different levels of complexity and exhibit different levels of attractiveness to the public. Setmakers may manufacture various types of decoders for different cost prices, inter alia by using different amounts of memory. Type-1 decoders merely gather the few relevant data items to be displayed and present them in a manner defined by the decoder manufacturer, i.e. the setmaker. Type-2 decoders have additional means to allow the user to navigate through the plurality of data items. These navigation means, and hence the in attractiveness, are also setmaker-defined. Type-3 decoders comply completely with the transmitted display format and navigation instructions, if any.
The EPG standard provides some form of compatibility between different types of decoders and different types of transmission. For example, a type-2 decoder without appropriate means for receiving and processing presentation and navigation data may nevertheless be adapted to receive EPG type-3 information. Such a decoder will ignore the transmitted presentation and navigation data, and present and navigate through the information in a locally defined manner.